Abstract

In the course of the research on yellow fever at the Institute of Tropical Hygiene at Amsterdam (1), the question arose also with us about the relationship between yellow fever and dengue. At first we were struck by the great resemblance to dengue, as regards temperature-chart and the subjective symptoms in a case of laboratory infection with yellow fever. Later on we found that a remarkable difference exists between adult cynomolgi and nemestrini from the Malay Archipelago, that as a rule appeared to be resistant against the yellow fever virus (the so called “souche française” from Dakar) and adult rhesi from the Northern part of India, who were extremely susceptible. And lastly, this same difference appeared to exist between adult Indian cynomolgi and very young animals of the same species, which we found just as susceptible as the rhesi. Especially the latter fact seemed to plead for an immunity acquired during life.